Abstract: For studying transient unstable flow variation in centrifugal pump impeller with cavitation, steady and transient calculations with cavitation taking place in centrifugal pump impeller were carried out by using ANSYS-CFX software. The transient nonlinear flow in flow channel was analyzed by applying the calculation results of the velocity field, the pressure field, the gas volume fraction and the pressure fluctuation of the different flow channels in the pump. The research results show that influenced by rotor-stator interference, volute throat area and other factors, the cavitation developing in each channel of centrifugal pump impeller is nonlinear. With the development of cavitation, the distributions of pressure field, velocity field and gas volumetric fraction of the impeller interior are asymmetrical. The main reason leading to this kind of nonlinear cavitation phenomenon is the asymmetry of the spiral case structure and the non synchronous of the cavitation process in the flow channel region from the middle surface in the flow channel to the back of the blade. In case of no significant cavitation, pulsating flow of different flow channels depicts the same regularity, but the main frequency of the pressure fluctuation is chaotic and the regularity is weakened under the condition of severe cavitation.